<!doctype html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .app {
            margin: 20px;
            height: 100px;
            width: 100px;
            float: left;
            background-color: #eee;
            border-radius: 20px;
            box-shadow: 4px 4px 4px 0px rgba(0, 0, 0, 0.18), -4px -4px 4px #fff;
            cursor: pointer;
            transition: width .2s ease-out;
        }
        .app:hover{
            box-shadow: inset 4px 4px 4px 0px rgba(0, 0, 0, 0.18), inset -4px -4px 5px #fff;
        }
    </style>
</head>
<body bgcolor="#eee">
<div style="width: 600px; margin: 100px auto;">
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
    <div class="app"></div>
</div>
</body>
</html>